JLG 340AJ Service Manual - Manual (Page 220)

SECTION 5 - HYDRAULICS
5-62 – JLG Lift – 3121259
Table 5-11. System Operating Hot
Item Description Action
Oil level in reservoir Insufficient hydraulic fluid does not meet cooling
demands of system Fill reservoir to proper level.
Heat exchanger Heat exchanger is not sufficiently cooling the system Check air flow and input air temperature for heat
exchanger. Clean, repair or replace heat exchanger.
Charge pressure Low charge pressure overworks system Measure charge pressure. Inspect and adjust or replace
charge relief valve. Inspect charge pump. Repair or replace
charge pump.
Charge pump inlet vacuum High inlet vacuum overworks system. A dirty filter
increases the inlet vacuum. Inadequate line size will
restrict flow Check charge inlet vacuum. If high, inspect inlet filter and
replace as necessary. Check for adequate line size, length
or other restrictions.
System relief pressure settings If the system relief valves are worn, contaminated, or valve
settings are too low, the relief valves get overworked Verify settings of pressure limiters and high pressure relief
valves and adjust or replace as necessary.
System pressure Frequent or long term operation over system relief setting
creates heat in system Measure system pressure. If pressure is too high, reduce
loads.
Table 5-12. System Noise Or Vibration
Item Description Action
Reservoir oil level Low oil level leads to cavitation Fill reservoir.
Aeration of the oil/pump inlet vacuum Air in system decreases efficiency of units and controls. Air
in system is indicated by excessive noise in pump, foaming
in oil, and hot oil. Find location where air is entering into the system and
repair. Check that inlet line is not restricted and is proper
size.
Cold oil If oil is cold, it may be too viscous for proper function and
pump cavitates Allow the oil to warm up to its normal operating tempera-
ture with engine at idle speed
Pump inlet vacuum High inlet vacuum causes noise/cavitation Check that inlet line is not restricted and is proper size.
Check filter and bypass switch.
Shaft couplings A loose shaft coupling causes excessive noise Replace loose shaft coupling.
Shaft alignment Misaligned pump and prime mover shafts create noise Align shafts.
Charge/system relief valves Unusual noise may indicate sticking valves. Possible con-
tamination Clean/replace valves and test pump.